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I have pictured the entire
mill here for visual reference as you look at the remaining illustrations.
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First, you have to decide what kind of frame
to mount your mill on. I simply made a rectangle with 2 X 4's and screwed
two layers of 1/2 inch plywood on top. Lloyd's plan provides all the patterns to build
a nice milling cabinet with its own stand. Whatever you use, it must be very sturdy!!
These mills must endure heavy vibration and weight loads.
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The electric motor should be a 1/3 to 1/2
horsepower, capacitor-start, 1725 rpm, 115v motor. You can get one from
Grainger using part # 6K758. In my case, I am using a motor salvaged from a washing
machine for which I paid $10. Since it has coils for 2 speeds, I used 2 switches.
One switches between hi and low speed and the other is the on/off switch. It turned
out that I only use the fast speed, so the speed switch is superfluous. The shaft
sheave on the motor should be 2 inch o.d. by 1/2 inch (Grainger #3X895).
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The drive shaft for the mill is 5/8 inch
round steel bar stock. These can be purchased at any hardware store. Be sure
it is perfectly straight. The sheave on the drive shaft is a 6 inch o.d. by 5/8
inch (Grainger #3X919). This cost me $3.72. You will also need two self-centering
ball-bearing pillow-block bearings to mount the drive shaft (Grainger #2X898). I
had to sand the drive shaft a little bit to allow the bearings to slide onto the shaft.
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Before placing the bearings on the shaft,
you need to place a piece of automotive heater hose on it as shown here.
This hose is 5/8 inch i.d. by 7/8 inch o.d. It can be found at most hardware or
auto parts stores. A little lubrication of some kind on the shaft will greatly
aid the sliding on of the hose.
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The other
side of the mill jar cradle uses a ball bearing equipment roller. I bought this
one at Woodworker's Warehouse for about $10. This picture shows the roller removed
from its bracket. The roller has been covered with two layers of bicycle tire
inner tube. The inner tube layers have been folded back in the picture for
illustrative purposes only. You may be wondering how to get the inner tube layers
over the roller. Again, Lloyd describes a technique which works very
nicely.
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Start with a 26 inch by 2 inch bicycle
tire inner tube. Cut the deflated tube about 3 inches from the valve stem and tightly tie a cord
around each end so the tube can be inflated to look like a long three inch diameter
sausage. The trick is to push the roller end into the end of the inflated inner tube.
When the roller is completely enclosed by the inner tube with a few inches of overlap,
you can cut the sausage off near the valve stem to allow it to deflate. You now have
two layers of rubber over the roller which are connected at one end. After allowing
the rubber to relax a little bit, you can now trim the ends with scissors to within
1/4 inch of the ends of the roller. Now re-install the roller in its bracket and check
for unimpeded rotation.
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If you mount the drive shaft and equipment roller
perfectly parallel, your mill jar may not creep as it rolls in the
cradle. To be safe, I installed this bumper to prevent the mill jar from exiting its cradle.
I used two Teflon furniture slides on the bumper to allow the mill jar to slide against the
bumper with little friction. The drive shaft and equipment roller are mounted with 3 inches
of space between them to accommodate both a 4 inch and 5 inch mill jar. A 6 inch mill jar
requires a space of 4.5 inches.
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This is a mill jar which has been constructed from
5 inch PVC pipe and fittings. The milling media is antimony
hardened, 3/4 inch lead balls. The construction of the jars is relatively simple, but
is a subject for another project page.
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Finally, this shot shows the placement of
the 5 inch mill jar in the cradle. With this setup, I can mill about 3 1/4
cups of high quality black powder in about 3 hours. The efficiency of this mill
is dependent upon many factors which are explained in Lloyd's book. There is a
wealth of information about milling theory contained in the book and I would highly
recommend the serious pyrotechnician to purchase it. You can find it in the
books section of Skylighter's web catalog.
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